Can someone explain 240p and NTSC to me?

[Fishaman P]

That already is the original data straight from the TV.

In 240p, you're running approx. 60 frames per second interlaced with black lines to make up for the resolution, in 480i, you run the video slower, at approx. 30FPS, but with two "original frames" on-screen at the same time, they're interlaced with each other.

The amount of actual original frames is exactly the same - to get the 240p @ 60FPS video, you de-interlace the 480i video so that you isolate the two frames from one picture.

So you're saying that if the source is 240p, but I'm trying to capture as 480i, there will never be any scanlines captured?
If so, I think that solves this.

 

[Foxi4]

So you're saying that if the source is 240p, but I'm trying to capture as 480i, there will never be any scanlines captured?
If so, I think that solves this.

The scanlines are "created" by the CRT itself - since the line wasn't updated, it dims away a bit, but never fully. It's a physical property of the screen itself. Run a retro system on a modern LCD television and it won't even grace you with scanlines at all.

 

[Fishaman P]

The scanlines are "created" by the CRT itself - since the line wasn't updated, it dims away a bit, but never fully. It's a physical property of the screen itself. Run a retro system on a modern LCD television and it won't even grace you with scanlines at all.

I think that just about sums it up. Thanks for teaching me!

 

[RodrigoDavy]

It
However, when capturing videos of 240p material on a PC, you capture at 29.97 fields per second. I'm also told that you can deinterlace to get the lossless source. I simply don't see how that can be true. Aren't you getting half black during that time? How can you recover all the original data? Or is it just not lossless?

240p =/= 240i =/= 480i =/= 480p

If you captured in 240p it means the material you have got is already progessive, you can not use deinterlacing because you obviously can only use deinterlacing in interlaced video recorded in 240i, 480i or 1080i. (Yes, you can capture digital video in interlaced form, in fact many DVDs have interlaced recording especially when they have TV material)

If you're capturing NTSC signal at 240p and 29,97fps it means the signal you got basically is ignoring half the fields in the NTSC signals, this is still a kind of deinterlacing although it produces a bad quality video.

If you're capturing NTSC signal at 480p and 29,97fps it means you're transforming every 2 interlaced fields in 1 progressive frame. This way you get the correct resolution but only half the fps. One thing that many people don't understand is that 2 interlaced fields DOES NOT EQUAL one progressive frame. Each interlaced field is capture in different time intervals which means when the second field is captured the scene recorded is already different timewise than the first one. In other words you're going to get a lot of visual artifacts that will make the video look shitty in quality.

By using complex deinterlacing algorithms you capture a 480p and 59,94 fps from a NTSC signal. Basically what is done is that you replace the black lines in the NTSC signal with computer generated guesses of what the lines would be like if they existed.

I recommend reading these:

http://en.wikipedia.org/wiki/Interlaced_video
http://en.wikipedia.org/wiki/Deinterlacing